Timewalking is indeed super fun. I wouldn't mind seeing it extended to raids either although I imagine that's a way off yet.
Mythic Dungeons are also good, although it looks like they're being replaced by that Greater Rift-esque system in Legion? If it keeps dungeons relevant through the expansion that'd be nice, especially if the loot stacks up against raiding.
Supposedly the idea behind the greater rift style dungeons is that you can get 1 really good piece of loot per week depending on how high you can get. If you get the best reward possible it should be Mythic ilevel. I think just clearing a dungeon gives loot too, but not as high ilevel.
Same idea with PvP, if you are good at rated PvP you can get gear that stacks up against raid gear, but no trinkets or set bonuses from PvP gear (that's all basically built into the PvP talent system)